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Here’s the 23z sounding from RDU (Raleigh-Durham, NC.)
The sounding suggests mostly snow, as the entire column is at or below freezing, but boundary layer temperatures remain marginal, right around 32F. But notice there really isn’t much CI signal, as 850-500mb lapse raters are moist adiabatic (~4.00 C/km), CAPE is virtually non-existent, TT’s are below 40, and Showalter indices are running in the lower teens. Per NEXRAD pics from the CAE, and a wider view of the situation from Intellicast, there appears to be stronger convection associated with an area of enhanced UVM across northern South Carolina that’s progressing northward into North Carolina, as the dry slot fills in.
http://www.intellicast.com/Local/USLoca ... e&pid=none
This new area of convection is associated with an area of stronger PVA and UVM ahead of the s/w and upper level support back to the southwest. If we look at the sounding out of CHS (Charleston, SC) though, we have a lot different of a story.
Some weak CAPE is present, lapse rates are dry adiabatic (about 6.00 C/km), TT’s are running in the 47 range, and Showalter indices are much lower also, which would support some weak/elevated convection.
Freezing rain will still be a problem in what’s left of the dry slot, as sufficient drying may take place as UVM slackens off to drop the relative humidity in the dendritic layer, resulting in mostly light freezing drizzle or some sleet, in areas where it had been snowing with the first area of precipitation that moves north earlier in the day.
Over the next few hours increasing isentropic lift and intensifying low level frontogenesis in association with the development of the coastal front will help to increase precipitation rates, and produce heavier snowfall later on this evening and overnight tonight. Most of the data would support good lift and saturation within the dendritic layer, so, I really don’t think there will be any problem getting at least 10:1 ratios in and around the Raleigh Durham area, on northwest, even in spite of the marginal boundary layer temperatures. Probably going to be some good CSI/mesoscale precipitation banding further north back in the cold air where EPV is lower.
In general, I still feel that Albemarle to Raleigh corridor is set up for about 6-12 inches.
For you guys in Washington DC, and Baltimore, it was ever so close, but just not close enough. As you can clearly see there is some virga on radar just to the south of the metro areas getting close to Fredericksburg. I don’t think anything will reach the ground.
As far as the last remaining “what if” goes, if the 500mb low was closed off with two or three contours, and below 549dm, it probably would probably be able to turn more northeast than east, and come up. But as of right now, I don’t see that being a possibility.
In addition to that, strong winds will affect the North Carolina coast through tomorrow afternoon. This will probably be more severe for the because because of the low's track which takes it north to a point, then due east out to sea underneath the block which keeps coastal sections on the northwest flank in the strong northeasterly flow. This could be worse especially if we see some kind of rouge development.
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